10 files changed, 75 insertions, 7 deletions

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index d9ecceea5a02..43e0816d0de1 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -3627,6 +3627,23 @@ struct {
 
 KVM handlers should exit to userspace with rc = -EREMOTE.
 
+7.5 KVM_CAP_SPLIT_IRQCHIP
+
+Architectures: x86
+Parameters: None
+Returns: 0 on success, -1 on error
+
+Create a local apic for each processor in the kernel. This can be used
+instead of KVM_CREATE_IRQCHIP if the userspace VMM wishes to emulate the
+IOAPIC and PIC (and also the PIT, even though this has to be enabled
+separately).
+
+This supersedes KVM_CREATE_IRQCHIP, creating only local APICs, but no in kernel
+IOAPIC or PIC. This also enables in kernel routing of interrupt requests.
+
+Fails if VCPU has already been created, or if the irqchip is already in the
+kernel (i.e. KVM_CREATE_IRQCHIP has already been called).
+
 
 8. Other capabilities.
 ----------------------
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index a0ef289d5a86..befcf555bddc 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -684,6 +684,8 @@ struct kvm_arch {
         u32 bsp_vcpu_id;
 
         u64 disabled_quirks;
+
+        bool irqchip_split;
 };
 
 struct kvm_vm_stat {
diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index f90952f64e79..08116ff227cc 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -35,6 +35,7 @@
 #include <linux/kvm_host.h>
 #include <linux/slab.h>
 
+#include "ioapic.h"
 #include "irq.h"
 #include "i8254.h"
 #include "x86.h"
@@ -333,7 +334,8 @@ static void create_pit_timer(struct kvm *kvm, u32 val, int is_period)
         struct kvm_kpit_state *ps = &kvm->arch.vpit->pit_state;
         s64 interval;
 
-        if (!irqchip_in_kernel(kvm) || ps->flags & KVM_PIT_FLAGS_HPET_LEGACY)
+        if (!ioapic_in_kernel(kvm) ||
+            ps->flags & KVM_PIT_FLAGS_HPET_LEGACY)
                 return;
 
         interval = muldiv64(val, NSEC_PER_SEC, KVM_PIT_FREQ);
diff --git a/arch/x86/kvm/ioapic.h b/arch/x86/kvm/ioapic.h
index bf36d66a1951..a8842c0dee73 100644
--- a/arch/x86/kvm/ioapic.h
+++ b/arch/x86/kvm/ioapic.h
@@ -97,6 +97,14 @@ static inline struct kvm_ioapic *ioapic_irqchip(struct kvm *kvm)
         return kvm->arch.vioapic;
 }
 
+static inline int ioapic_in_kernel(struct kvm *kvm)
+{
+        int ret;
+
+        ret = (ioapic_irqchip(kvm) != NULL);
+        return ret;
+}
+
 void kvm_rtc_eoi_tracking_restore_one(struct kvm_vcpu *vcpu);
 bool kvm_apic_match_dest(struct kvm_vcpu *vcpu, struct kvm_lapic *source,
                 int short_hand, unsigned int dest, int dest_mode);
diff --git a/arch/x86/kvm/irq.h b/arch/x86/kvm/irq.h
index 9e6e7e04de98..2f9703dcd913 100644
--- a/arch/x86/kvm/irq.h
+++ b/arch/x86/kvm/irq.h
@@ -83,13 +83,22 @@ static inline struct kvm_pic *pic_irqchip(struct kvm *kvm)
         return kvm->arch.vpic;
 }
 
+static inline int irqchip_split(struct kvm *kvm)
+{
+        return kvm->arch.irqchip_split;
+}
+
 static inline int irqchip_in_kernel(struct kvm *kvm)
 {
         struct kvm_pic *vpic = pic_irqchip(kvm);
+        bool ret;
+
+        ret = (vpic != NULL);
+        ret |= irqchip_split(kvm);
 
         /* Read vpic before kvm->irq_routing.  */
         smp_rmb();
-        return vpic != NULL;
+        return ret;
 }
 
 static inline int lapic_in_kernel(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
index 9efff9e5b58c..67f6b62a6814 100644
--- a/arch/x86/kvm/irq_comm.c
+++ b/arch/x86/kvm/irq_comm.c
@@ -208,7 +208,7 @@ void kvm_free_irq_source_id(struct kvm *kvm, int irq_source_id)
                 goto unlock;
         }
         clear_bit(irq_source_id, &kvm->arch.irq_sources_bitmap);
-        if (!irqchip_in_kernel(kvm))
+        if (!ioapic_in_kernel(kvm))
                 goto unlock;
 
         kvm_ioapic_clear_all(kvm->arch.vioapic, irq_source_id);
@@ -328,3 +328,10 @@ int kvm_setup_default_irq_routing(struct kvm *kvm)
         return kvm_set_irq_routing(kvm, default_routing,
                                    ARRAY_SIZE(default_routing), 0);
 }
+
+static const struct kvm_irq_routing_entry empty_routing[] = {};
+
+int kvm_setup_empty_irq_routing(struct kvm *kvm)
+{
+        return kvm_set_irq_routing(kvm, empty_routing, 0, 0);
+}
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index c4bcc86d6dc4..e05946c36b87 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -209,7 +209,8 @@ out:
         if (old)
                 kfree_rcu(old, rcu);
 
-        kvm_vcpu_request_scan_ioapic(kvm);
+        if (ioapic_in_kernel(kvm))
+                kvm_vcpu_request_scan_ioapic(kvm);
 }
 
 static inline void apic_set_spiv(struct kvm_lapic *apic, u32 val)
@@ -1845,7 +1846,8 @@ void kvm_apic_post_state_restore(struct kvm_vcpu *vcpu,
                 kvm_x86_ops->hwapic_isr_update(vcpu->kvm,
                                 apic_find_highest_isr(apic));
         kvm_make_request(KVM_REQ_EVENT, vcpu);
-        kvm_rtc_eoi_tracking_restore_one(vcpu);
+        if (ioapic_in_kernel(vcpu->kvm))
+                kvm_rtc_eoi_tracking_restore_one(vcpu);
 }
 
 void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 28c98c8f9d1c..f720774a4797 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2448,6 +2448,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
         case KVM_CAP_ENABLE_CAP_VM:
         case KVM_CAP_DISABLE_QUIRKS:
         case KVM_CAP_SET_BOOT_CPU_ID:
+        case KVM_CAP_SPLIT_IRQCHIP:
 #ifdef CONFIG_KVM_DEVICE_ASSIGNMENT
         case KVM_CAP_ASSIGN_DEV_IRQ:
         case KVM_CAP_PCI_2_3:
@@ -3555,6 +3556,24 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
                 kvm->arch.disabled_quirks = cap->args[0];
                 r = 0;
                 break;
+        case KVM_CAP_SPLIT_IRQCHIP: {
+                mutex_lock(&kvm->lock);
+                r = -EEXIST;
+                if (irqchip_in_kernel(kvm))
+                        goto split_irqchip_unlock;
+                if (atomic_read(&kvm->online_vcpus))
+                        goto split_irqchip_unlock;
+                r = kvm_setup_empty_irq_routing(kvm);
+                if (r)
+                        goto split_irqchip_unlock;
+                /* Pairs with irqchip_in_kernel. */
+                smp_wmb();
+                kvm->arch.irqchip_split = true;
+                r = 0;
+split_irqchip_unlock:
+                mutex_unlock(&kvm->lock);
+                break;
+        }
         default:
                 r = -EINVAL;
                 break;
@@ -3668,7 +3687,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
                 }
 
                 r = -ENXIO;
-                if (!irqchip_in_kernel(kvm))
+                if (!irqchip_in_kernel(kvm) || irqchip_split(kvm))
                         goto get_irqchip_out;
                 r = kvm_vm_ioctl_get_irqchip(kvm, chip);
                 if (r)
@@ -3692,7 +3711,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
                 }
 
                 r = -ENXIO;
-                if (!irqchip_in_kernel(kvm))
+                if (!irqchip_in_kernel(kvm) || irqchip_split(kvm))
                         goto set_irqchip_out;
                 r = kvm_vm_ioctl_set_irqchip(kvm, chip);
                 if (r)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 1bef9e21e725..354f147647ab 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1002,6 +1002,7 @@ static inline int mmu_notifier_retry(struct kvm *kvm, unsigned long mmu_seq)
 #endif
 
 int kvm_setup_default_irq_routing(struct kvm *kvm);
+int kvm_setup_empty_irq_routing(struct kvm *kvm);
 int kvm_set_irq_routing(struct kvm *kvm,
                         const struct kvm_irq_routing_entry *entries,
                         unsigned nr,
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index a9256f0331ae..ed00f8fc9ea2 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -824,6 +824,7 @@ struct kvm_ppc_smmu_info {
 #define KVM_CAP_MULTI_ADDRESS_SPACE 118
 #define KVM_CAP_GUEST_DEBUG_HW_BPS 119
 #define KVM_CAP_GUEST_DEBUG_HW_WPS 120
+#define KVM_CAP_SPLIT_IRQCHIP 121
 
 #ifdef KVM_CAP_IRQ_ROUTING